Many types of air-born bodies, both powered and unpowered, include a glide capability to increase the body's range. This is particularly the case with munitions, such as bombs, rockets, or missiles, for which a greater standoff range is desirable. Greater standoff range enhances pilot and aircraft survivability. A longer range also provides additional opportunities for maneuvering of the air-born body during flight.
Increasing the range of an air-born body can be achieved through extendable wings that are deployed during flight. Before flight, these wings are stowed either within the body itself, or within a small volume that fits within the body's storage footprint. In one type of deployable range extension wings, the wings are hinged at the root to the body's fuselage. In the stowed position, the wings lie generally parallel to and against the fuselage. During deployment, the wings pivot outwardly to provide a swept wing configuration. Efficient packaging during storage is particularly important to minimize drag and range loss in the case of externally carried weapons. For internally stored weapons, payloads should be maximized with minimum volume. However, designing a deployable wing that offers high efficiency, small packaging volume, and low cost is challenging.
A joined or “diamond” wing configuration offers benefits for deployable range extension wings. In this configuration, two extending wings are attached together via a pivot at a common wing tip. This arrangement offers a compact packaging as the wings are folded closely together during storage. After deployment, the triangular wing configuration provides greater strength and stiffness than does a single wing of comparable span or area. As one wing bends or twists, the attached wing also must bend or twist, and the net effect of the bending-twisting coupling is improved structural performance. Improved structural margins allow a higher degree of maneuverability without overstressing the wings.
U.S. Pat. No. 5,615,846 discloses a joined wing range extension kit called a “diamond back.” This extended wing has been shown to successfully increase the range of an air-born body. There are disadvantages with the diamond back type of wing also. The diamond back is a complex mechanism and expensive to manufacture. The external packaging volume needed to house the mechanism is considerable. To maximize strength and stiffness in a narrow profile, the wings are CNC machined from stainless steel, which has three times the density of aluminum and has a high radar signature. Mechanically actuated ailerons have additionally been used to provide roll control.